I. Field of the Invention
The present invention relates to welding materials for arc welding and is particularly concerned with a flux composition for flux-cored wires for welding and surfacing steels with a gas-shielded process.
The invention is of particular advantage in the case of flux-cored wires for automatic and semiautomatic welding in all weld positions.
2. Prior Art
There are known flux compositions used to form a core in flux-cored wires for welding steel and surfacing the same with the CO.sub.2 process in all weld positions, comprising a steel sheath filled with a powdered welding flux. In particular, the best welding properties are featured by a flux-cored wire having a flux core containing the following ingredients, by weight %:
manganese-silicon: 10-25 PA1 ferromanganese: 1-7 PA1 iron powder: 2-40 PA1 sodium fluoride: 0.5-3 PA1 potassium silicate: 0.5-3 PA1 titanium dioxide: 30-60 PA1 aluminium-magnesium alloy: 1-7 PA1 manganese oxide: 3-10 PA1 aluminium powder: 0.5-5.0 PA1 rutile concentrate: 53.4 PA1 manganese dioxide: 4.4 PA1 silicon dioxide: 3.0 PA1 sodium dioxide: 3.0 PA1 magnetite: 6.0 PA1 ferromanganese: 13.0 PA1 ferrosilicon: 12.0 PA1 rutile concentrate: 20-53 PA1 ferromanganese: 10-22.8 PA1 ferrosilicon: 1.3-6 PA1 sodium fluosilicate: 1-5 PA1 calcined magnesite: 1.3-10 PA1 electrocorundum: 1.6-7.5 PA1 iron powder: balance
(cf. U.S. Pat. No. 3,818,178)
The presence in the above flux composition of aluminium and magnesium which form a number of oxides makes it possible to obtain a quality welding slag ensuring a proper formation of the weld. However, the weld thus produced contains a part of aluminium in the form of nitride, which is known to shift a cold shortness threshold to the range of high temperatures. This disadvantage is responsible for the above flux-cored wire having a limited application.
There are also known flux compositions whose cold shortness threshold lies in the range of low temperatures (-20.degree. C.). The best welding properties in this case are manifested by a flux-cored wire having a core composition containing the following ingredients, by weight %:
(cf. U.S. Pat. No. 3,800,120).
It has been established, however, that the weld produced by using a flux-cored wire having a core composed of the above flux ingredients contains a considerable amount of oxygen (0.09 by weight %) and hydrogen (10-12 cm.sup.3 per 100 g of the weld metal) which lowers resistance of the weld metal with regard to the formation of hot cracks and the weld notch impact strength at low temperatures. To ensure rapid crystallization of welding slags resulting from melting of the flux-cored wire, and to improve the formation of the weld, a considerable amount of silica is added to the above flux, with the silica content in the weld metal constituting up to 0.8% by weight, which affects plasticity thereof.
The invention resides in the provision of a flux composition for a flux-cored wire for use in surfacing and welding steels with a gas-shielded process, which flux due to a properly selected ingredients improves welding properties of the fluxcored wire and ensures that the hydrogen and oxygen content in the weld metal is as low as possible, thereby imparting thereto improved mechanical properties within a wide range of temperatures.
The principal object of the invention is to provide a flux composition for a flux-cored wire for welding and surfacing steels with a gas-shielded process, which flux composition improves welding properties of the flux-cored wire and ensures that hydrogen and oxygen content be minimized, thereby imparting to the said flux-cored wire improved mechanical properties within a wide range of temperatures.
Another object of the invention is to enhance efficiency of the welding process.
Still another object of the invention is to produce void-free weld metal.
Yet another object of the invention is to obtain weld metal having a minimized amount of non-metallic inclusions.
A further object of the invention is to lower fluidity of the molten slag while welding, and to thereby improve conditions for the formation of the weld metal.
Other objects, advantages and features of the invention will become evident from the following description thereof.